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<h1>GoJS Brushes</h1>
<p>
A <a>Brush</a> holds color information and describes how to draw the inside of a Shape or the stroke of a shape or a TextBlock or the background of any GraphObject.
<p>
A Brush must not be modified once it has been assigned to a GraphObject, such as the <a>Shape.fill</a> or <a>TextBlock.stroke</a> or <a>GraphObject.background</a>. However, a Brush may be shared by multiple GraphObjects.


<h2 id="SolidBrushes">Solid Brushes</h2>

The simplest brushes are defined by a single solid color. Because they are so simple, anywhere you want a single-color brush you can subsitute a valid CSS color string.

<pre class="lang-js" id="simpleBrushes">
  diagram.add($(go.Part,
      $(go.Shape, "Circle", {
        fill: $(go.Brush, { color: "palegreen" })
      })
    ));

  diagram.add($(go.Part,
      $(go.Shape, "Circle", {
        fill: "palegreen"
      })
    ));
</pre>
<script>goCode("simpleBrushes", 600, 120)</script>

<p>Many CSS color strings are valid, including named colors, hex values, RGB values, and RGBA values.

<pre class="lang-js" id="simpleBrushes2">
  diagram.layout = $(go.GridLayout);

  diagram.add($(go.Part,
      $(go.Shape, "Circle", {
        fill: "#DFAD83"
      })
    ));

  diagram.add($(go.Part,
      $(go.Shape, "Circle", {
        fill: "rgba(0,255,0,.3)" // semi transparent green
      })
    ));

  diagram.add($(go.Part,
      $(go.Shape, "Circle", {
        fill: "rgba(0,255,0,.3)",
        stroke: '#DFBB00',
        strokeWidth: 4,
        background: 'coral'
      })
    ));
</pre>
<script>goCode("simpleBrushes2", 600, 120)</script>


<h2 id="GradientBrushes">Gradient Brushes</h2>

<p>Gradient brushes are defined by setting the type and adding a number of color stops to the Brush.</p>
<pre class="lang-js">
  // constructs a Linear gradient brush
  var brush = new go.Brush(go.Brush.Linear);
  brush.addColorStop(0, "blue");
  brush.addColorStop(1, "red");
</pre>

<p>To simplify the syntax, you can use go.GraphObject.make (see <a href="buildingObjects.html">building objects</a>):
<pre class="lang-js">
  // constructs the same Brush
  var brush = $(go.Brush, "Linear", { 0.0: "blue", 1.0: "red" });
</pre>

<p>Some examples follow:</p>

<pre class="lang-js" id="gradients1">
  diagram.add(
    $(go.Part, "Table",
      $(go.Shape, { row: 0, column: 0,
                    figure: "Circle", width: 100, height: 100, margin: 5,
                    // A linear gradient brush from blue to red, going from top to bottom (default)
                    fill: $(go.Brush, "Linear", { 0.0: "blue", 1.0: "red" })
                  }),

      $(go.Shape, { row: 0, column: 1,
                    figure: "Circle", width: 100, height: 100, margin: 5,
                    // A linear gradient brush from blue to red, going from bottom to top
                    // by defining start and end spots
                    fill: $(go.Brush, "Linear", { 0.0: "blue", 1.0: "red", start: go.Spot.Bottom, end: go.Spot.Top })
                  })
    ));
</pre>
<script>goCode("gradients1", 600, 120)</script>

<p>Brushes can have any number of color stops:</p>

<pre class="lang-js" id="gradients2">
  diagram.add(
    $(go.Part, "Table",
      $(go.Shape, { row: 0, column: 0,
                    figure: "Rectangle", width: 100, height: 100, margin: 5,
                    // A rainbow linear gradient brush:
                    fill: $(go.Brush, "Linear", {
                      0.0: "rgba(255, 0, 0, 1)",
                      0.15: "rgba(255, 255, 0, 1)",
                      0.30: "rgba(0, 255, 0, 1)",
                      0.50: "rgba(0, 255, 255, 1)",
                      0.65: "rgba(0, 0, 255, 1)",
                      0.80: "rgba(255, 0, 255, 1)",
                      1: "rgba(255, 0, 0, 1)"
                    })
                  }),

      $(go.Shape, { row: 0, column: 1,
                    figure: "Rectangle", width: 100, height: 100, margin: 5,
                    // A rainbow radial gradient brush:
                    fill: $(go.Brush, "Radial", {
                      0.0: "rgba(255, 0, 0, 1)",
                      0.15: "rgba(255, 255, 0, 1)",
                      0.30: "rgba(0, 255, 0, 1)",
                      0.50: "rgba(0, 255, 255, 1)",
                      0.65: "rgba(0, 0, 255, 1)",
                      0.80: "rgba(255, 0, 255, 1)",
                      1: "rgba(255, 0, 0, 1)"
                    })
                  })
    ));
</pre>
<script>goCode("gradients2", 600, 120)</script>

<p>Radial gradient brushes can be controlled with <a>Brsuh.startRadius</a> and <a>Brush.endRadius</a>, which default to zero and NaN, respectively, meaning the gradient begins at the very center and goes to the farthest measured edge of the object.

<pre class="lang-js" id="gradients21">
  diagram.layout = $(go.GridLayout);

  diagram.add(
    $(go.Part,
      $(go.Shape, {
                    figure: "Rectangle", width: 100, height: 100, margin: 5,
                    // A rainbow radial gradient brush:
                    fill: $(go.Brush, "Radial", {
                      0.0: "red", 1: "black"
                    })
                  })
    ));

  diagram.add(
    $(go.Part,
      $(go.Shape, {
                    figure: "Rectangle", width: 100, height: 100, margin: 5,
                    // A rainbow radial gradient brush:
                    fill: $(go.Brush, "Radial", {
                      startRadius: 30, 0.0: "red", 1: "black"
                    })
                  })
    ));

  diagram.add(
    $(go.Part,
      $(go.Shape, {
                    figure: "Rectangle", width: 100, height: 100, margin: 5,
                    // A rainbow radial gradient brush:
                    fill: $(go.Brush, "Radial", {
                      startRadius: 30, endRadius: 40, 0.0: "red", 1: "black"
                    })
                  })
    ));
</pre>
<script>goCode("gradients21", 600, 120)</script>



<p>Several GraphObjects can share the same Brush:

<pre class="lang-js" id="gradients3">

  diagram.layout = $(go.GridLayout);

  // Create one brush for several GraphObjects to share:
  var rainbow = $(go.Brush, "Linear", {
                        0.0: "rgba(255, 0, 0, 1)",
                        0.15: "rgba(255, 255, 0, 1)",
                        0.30: "rgba(0, 255, 0, 1)",
                        0.50: "rgba(0, 255, 255, 1)",
                        0.65: "rgba(0, 0, 255, 1)",
                        0.80: "rgba(255, 0, 255, 1)",
                        1: "rgba(255, 0, 0, 1)"
                      });
  diagram.add(
    $(go.Part,
      $(go.Shape, { figure: "Rectangle", width: 100, height: 100, fill: rainbow })
    ));

  diagram.add(
    $(go.Part,
      $(go.Shape, { figure: "Fragile", width: 50, height: 50, angle: 45, fill: rainbow })
    ));


  diagram.add(
    $(go.Part, "Auto",
      $(go.Shape, { figure: "Rectangle", fill: rainbow }),
      $(go.TextBlock, "text", { font: 'bold 32pt sans-serif', stroke: rainbow, angle: 90 })
    ));

  diagram.add(
    $(go.Part,
      $(go.Shape, { figure: "Circle", width: 70, height: 70, angle: 180, fill: null, strokeWidth: 10, stroke: rainbow })
    ));

</pre>


<script>goCode("gradients3", 600, 120)</script>


<h2 id="PatternBrushes">Pattern Brushes</h2>
<p>The following example sets up two Pattern brushes, one using an HTML Canvas with content drawn to it, which looks like this:
<div id="patternCanvas"></canvas>
<script type="text/javascript">
  // set up an 40x40 HTML Canvas and draw on it to create a repeating "tile" to use as a pattern
    var patternCanvas = document.createElement('canvas');
    patternCanvas.width = 40;
    patternCanvas.height = 40;
    var pctx = patternCanvas.getContext('2d');

    // This creates a shape similar to a diamond leaf
    pctx.beginPath();
    pctx.moveTo(0.0, 40.0);
    pctx.lineTo(26.9, 36.0);
    pctx.bezierCurveTo(31.7, 36.0, 36.0, 32.1, 36.0, 27.3);
    pctx.lineTo(40.0, 0.0);
    pctx.lineTo(11.8, 3.0);
    pctx.bezierCurveTo(7.0, 3.0, 3.0, 6.9, 3.0, 11.7);
    pctx.lineTo(0.0, 40.0);
    pctx.closePath();
    pctx.fillStyle = "rgb(188, 222, 178)";
    pctx.fill();
    pctx.lineWidth = 0.8;
    pctx.strokeStyle = "rgb(0, 156, 86)";
    pctx.lineJoin = "miter";
    pctx.miterLimit = 4.0;
    pctx.stroke();

    document.getElementById('patternCanvas').appendChild(patternCanvas);
</script>

<p>The other Pattern Brush uses this image:</p>
<p><img src="images/pattern.jpg"/></p>

<pre class="lang-js" id="diagramPre">

  // set up an 40x40 HTML Canvas and draw on it to create a repeating "tile" to use as a pattern
  function makePattern() {
    var patternCanvas = document.createElement('canvas');
    patternCanvas.width = 40;
    patternCanvas.height = 40;
    var pctx = patternCanvas.getContext('2d');

    // This creates a shape similar to a diamond leaf
    pctx.beginPath();
    pctx.moveTo(0.0, 40.0);
    pctx.lineTo(26.9, 36.0);
    pctx.bezierCurveTo(31.7, 36.0, 36.0, 32.1, 36.0, 27.3);
    pctx.lineTo(40.0, 0.0);
    pctx.lineTo(11.8, 3.0);
    pctx.bezierCurveTo(7.0, 3.0, 3.0, 6.9, 3.0, 11.7);
    pctx.lineTo(0.0, 40.0);
    pctx.closePath();
    pctx.fillStyle = "rgb(188, 222, 178)";
    pctx.fill();
    pctx.lineWidth = 0.8;
    pctx.strokeStyle = "rgb(0, 156, 86)";
    pctx.lineJoin = "miter";
    pctx.miterLimit = 4.0;
    pctx.stroke();

    return patternCanvas;
  }

  if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
  var $ = go.GraphObject.make;  // for conciseness in defining templates

  diagram.nodeTemplate =
    $(go.Node, "Spot",
      { resizable: true, resizeObjectName: 'SHAPE' },
      $(go.Shape, "Rectangle",
        { name: 'SHAPE', strokeWidth: 0, stroke: null },
        new go.Binding("fill")),
      $(go.TextBlock,
        { margin: 10, font: "bold 18px Verdana" },
        new go.Binding("text", "key"))
    );

  var img = new Image();
  img.src = 'images/pattern.jpg';

  // Use an image as a pattern
  var patternBrush = $(go.Brush, "Pattern", { pattern: img });
  // use a reference to an HTML Canvas (with renderings on it) as a pattern:
  var patternBrush2 = $(go.Brush, "Pattern", { pattern: makePattern() });


  diagram.model = new go.GraphLinksModel(
    [
      { key: "Alpha", fill: patternBrush },
      { key: "Beta",  fill: patternBrush2 }
    ],
    [
    ]);
</pre>
<div style="width:100%">
  <span id="diagramSpan" style="display: inline-block; vertical-align: top">
    <p><b>The result:</b></p>
  </span>
</div>
<script>goCode("diagramPre", 500, 300, go.Diagram, "diagramSpan");</script>

<h2 id="BrushFunctions">Brush Functions</h2>
<p>
  There are some functions available for generating different colors or modifying Brush colors:
</p>
<ul>
  <li>
    <a>Brush,randomColor</a> - returns a random hexadecimal color value
  <li>
    <a>Brush,lightenBy</a> and <a>Brush,darkenBy</a> - return lightened or darkened colors/brushes; there are both instance
    and static versions
  </li>
  <li>
    <a>Brush,lighten</a> and <a>Brush,darken</a> - convenience static functions which return lightened or darkened colors
  </li>
  <li>
    <a>Brush,mix</a> - mixes two colors together
  </li>
  <li>
    <a>Brush,isDark</a> - determines whether a color is dark, often used in bindings; there are both instance and static versions
  </li>
</ul>
<p>
  In the following example, parts use the lighten and darken functions to get suitable colors for their stroke/fill.
</p>
<pre class="lang-js" id="functions">
  diagram.layout = $(go.GridLayout);
  var color1 = "rgb(80, 130, 210)";
  var color2 = go.Brush.randomColor(192, 224);
  var gradBrush = $(go.Brush, "Linear", { 0: color1, 1: color2 });
  function shapeStyle() {
    return [ "Ellipse", { width: 120, height: 80, strokeWidth: 4 } ];
  }

  // static Brush methods
  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: color1, stroke: go.Brush.darken(color1) }),
      $(go.TextBlock, "dark stroke")));

  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: color1, stroke: go.Brush.darkenBy(color1, .4) }),
      $(go.TextBlock, "darker stroke")));

  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: go.Brush.lighten(color1), stroke: color1 }),
      $(go.TextBlock, "light fill")));

  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: go.Brush.lightenBy(color1, .4), stroke: color1 }),
      $(go.TextBlock, "lighter fill")));

  // instance Brush methods
  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: gradBrush.copy().lightenBy(.2) }),
      $(go.TextBlock, "lighter")));

  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: gradBrush }),
      $(go.TextBlock, "normal")));

  diagram.add($(go.Part, "Auto",
      $(go.Shape, shapeStyle(),
        { fill: gradBrush.copy().darkenBy(.2) }),
      $(go.TextBlock, "darker")));
</pre>
<script>goCode("functions", 600, 200)</script>
<p>
  In the following example, the color of text is determined by whether the background shape is dark.
</p>
<pre class="lang-js" id="functions2">
  diagram.layout = $(go.GridLayout);

  diagram.nodeTemplate =
    $(go.Node, "Auto",
      { desiredSize: new go.Size(80, 40) },
      $(go.Shape, "RoundedRectangle", { strokeWidth: 0 },
        new go.Binding("fill", "color")),
      $(go.TextBlock, { margin: 8 },
        new go.Binding("stroke", "color",
              // dark nodes use white text, light nodes use dark text
              function (c) { return go.Brush.isDark(c) ? "white" : "black"; }),
        new go.Binding("text", "key")
      )
    );

  diagram.model = new go.Model(
    [
      { key: "Alpha", color: "white" },
      { key: "Beta", color: "black" },
      { key: "Gamma", color: "darkblue" },
      { key: "Delta", color: "lightblue" },
      { key: "Epsilon", color: "darkgreen" },
      { key: "Zeta", color: "lightgreen" },
      { key: "Eta", color: "darkred" },
      { key: "Theta", color: "lightcoral" }
    ]
  )
</pre>
<script>goCode("functions2", 600, 200)</script>
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